1. Field of the Invention
The present invention relates to an air supply apparatus for an outboard motor, and more specifically to an apparatus for supplying air, fuel, power and control cables to the outboard motor (a small gasoline engine provided with a marine propulsion unit) liftably and steerably attached to a transom of a motorboat hull, even when the outboard motor sinks into water.
2. Description of the Prior Art
An example of prior-art air supply apparatus for outboard motors is disclosed in U.S. Pat. No. 4,375,356 entitled ARRANGEMENT FOR SUPPLYING AIR, FUEL, POWER AND CONTROL CABLES TO A MARINE PROPULSION UNIT by Stevens. FIGS. 1(A) and (B) show a Stevens' outboard motor. In these drawings, an outboard motor 9 is formed with a sealed power head (engine) compartment 5 and an engine cover 6 having a forwardly located cover wall 8, and composed of an internal combustion engine 9A, and a propulsion unit 9B having a propeller drive shaft 9C, a reversing transmission 9D and a propeller 9E. Further, the motor 9 is liftably and steerably attached to a transom 2 of a boat hull 1 via a mounting unit lA in such a way that the engine 9A communicates with the inside of the boat hull 1 through a flexible boot or duct 3 watertightly fixed between an aperture 4 formed in the transom 2 and an aperture 7 formed in the engine cover 6, as depicted in FIG. 1(B). Further, in FIG. 1(A), 1B denotes a swivel bracket and 1C denoted a steering axis.
In the above-mentioned prior-art air supply apparatus for an outboard motor, however, since the duct 3 is directly connected between the aperture 4 of the transom 2 and that 7 of the engine cover 6, when the duct 3 is connected to the engine cover 6 at a position away from the steering axis lC of the outboard motor 9, the duct 3 is moved together with the engine cover 6 whenever the propulsion unit 9B is pivoted for steering operation, thus resulting in a problem in that the durability of the duct 3 is poor. Further, even if the duct 3 is attached to the upper surface of the engine cover 6 at the steering axis 1C, there still exist a problem in that the duct is twisted whenever the propulsion unit 9B is pivoted for steering operation, so that the duct durability is still not satisfactory and further the external appearance is not good because the duct can easily be seen from outside.